The invention relates to apparatus and method for deboning meat of the type which separates meat from bony material by passing the meat radially through a sieve screen and the bony material axially through an outlet.
In the prior art meat deboning apparatus, an auger is utilized to compress and convey the meat and bone material axially through a sieve screen where the compressed meat passes through the sieve screen and the bony material is conveyed through an outlet at the end of the sieve screen For example, see US. Pat. Nos. 4,042,176 and 4,824,027. Some augers are made of a stainless steel with the flights of the auger welded to the root of the auger. Due to the properties of stainless steel, the metal infiltrates into the meat product more quickly than some other more suitable steels. The stainless steel is porous so that bacteria may find its way into the pores of the metal. In the welding process, if 100% penetration of the weld is not achieved, voids exist in the welds which harbor bacteria The bacteria harbored in the stainless steel material and in the welds can lead to uncleanliness. In reworking the fabricated augers, the presence of bacteria is quickly and obviously found by the stench emitted when heat is applied to the auger during reworking. It is not possible to wash out the fluids and bacteria retained in the welds and cracks during normal clean up procedures. Some prior art auger flights and roots have also been overlayed by welding with a hard surface material containing cobalt which is a contaminant. Due to the pliability of the base metal, the overlay will crack and allow metal to enter the meat product The prior art stainless steel has little wet abrasion resistance so that the edges of the flight erode inward beneath the hardened surface of the flights allowing the surface material to break off and damage the sieve screen. High chromium stainless steel is subject to hydrogen embrittlement which causes it to lose ductility and crack with shock. Further, cavitation will cause the protective film on high chromium stainless steel to be lost allowing erosion to rapidly take place and infiltrate metal into the product.
The helical flights on the prior art augers are either perpendicular to the axis of the auger or lean toward the exit end. This creates an impediment to radial flow on the front face of the flights and causes turbulence. The rear face is unable to retain product against it until the product reaches the outside diameter of the flight. Therefore, it cannot act as a slinger and impart maximum velocity to the product as it heads toward the screen. Meat and bone product is fed to the feed auger in an area which covers more than one auger flight. This allows pressure relief in the subsequent flights if the flight is full of product and centripetal force tends to push the product back up the entry pipe if it opens over a second or third flight. It has also been typical to use a shallow flight at the entry of the feed auger which reduces its loading capacity and the flight must cut off the product at the entry opening of the feed can more times for the same amount of infeed product thus increasing horse power requirements, as well as pulsing and cavitation. Typically, the feed auger is threaded into the motor coupling which creates assembly and disassembly problems and misalignment due to the threads cocking. In the typical meat deboning apparatus such as shown in U.S. Pat. No. 4,042,176 the auger must be provided in 2 sections, a feed auger and a compression auger for assembly in the unit. The feed and compression augers include auger roots with different tapers and flights with different configurations which do not produce the most efficient results. When the taper changes as the product passes from the feed auger to the compression auger, turbulence and cavitation cause a diminished product flow and increased temperature in the product. U.S. Pat. No. 4,638,954 discloses a compression auger having a root with a fairly uniform root section (FIG. 1) but the compression auger is one-piece and a separate feed auger is utilized in another section of the machine. U.S. Pat. No. 4,069,980 discloses a compression auger having a relatively uniform taper in combination with a feed auger where the feed and compression auger tapers are not constant. Typically, prior deboning apparatus have taught high pressures wherein compressive forces are exerted on the product from 1000 psi to above 10,000 psi which creates considerable problems in the functioning and proper sealing of the housings and bearings of the apparatus which can lead to overheated, inferior final meat product, and mechanical failure of the apparatus.
Accordingly, an important object of the present invention is to provide a meat deboning apparatus which operates at increased capacity and decreased temperatures and pressure for producing a better quality product.
Another object of the invention is to provide a meat deboning apparatus having an improved auger which includes a separate feed auger and a compression auger coupled as a unit wherein the auger has a constant taper over the entire length of the combined feed and compression auger and deep flights which handle increased amounts of product with reduced cavitation and temperature.
Another object of the present invention is to provide an improved meat deboning apparatus wherein the drive shaft of the apparatus is provided with improved bearings that allow the shaft to become self-aligned for more trouble free operation.
Another object of the invention is to provide a meat deboning apparatus having an improved auger which eliminates welding in the construction and is constructed from non-porous material so that the harboring of bacteria is reduced and the apparatus is more sanitary.
Still another important object of the present invention is to provide a meat deboning apparatus having an improved auger wherein the front faces of the flights of the auger are leaned rearward toward the entry end to prevent washing of the shear edges of the flights to provide superior shear action and meat separation in conjunction with the increased depth of the flights to increase production.
Still another important object of the present invention is to provide a meat deboning apparatus having an improved infeed opening to the entry end of the feed auger which, together with auger flights having increased depth and rearward tilt, provides a more efficient feeding of product at increased velocity of least 1.5 to 1 due to the orifice effect through the entry end of the feed auger and throughout the deboning housing.
Another object of the invention is to provide an improved meat deboning apparatus having improved coupling of the different shafts and auger sections in the apparatus so that they are self-aligning and require only a sliding fit which eliminate motor bearing failure, threads, and misalignment due to thread cocking.
Another object of the invention is to provide a meat deboning apparatus having an improved auger which includes feed auger and compression auger sections wherein the root of the feed and compression augers have a continuous taper so that the product does not have to change directions when passing from the feed auger to the compression auger simulating a one-piece auger without the problems associated with a one-piece auger such as weight and attendant cumbersome assembly and disassembly.
Another object of the present invention is to provide a meat deboning apparatus having a housing which contains a feed auger and a compression auger wherein the operating pressures within the housing are reduced so that the feed auger may be fed product more efficiently yet the production rate of the apparatus is still increased.
Yet another object of the invention is to provide a meat deboning apparatus having a front bar support assembly which maintains a front sliding block assembly in alignment which supports one end of the sieve screen.